It’s not uncommon to feel a little down during winter months. Days are shorter, temperatures are colder, and days off tend to be few and far between. For some people, however, seasonal changes bring on more serious mental health challenges that should not be ignored or dismissed.

Seasonal Affective Disorder (SAD) is a depressive disorder marked by sadness and symptoms that develop in a seasonal pattern. It affects as many as 10 million Americans, though many may not be aware that they suffer from it.

Like any depressive disorder, identifying the condition and ensuring individuals have the treatment and support they need is vital. Here are a few things to know about SAD and steps you can take to improve your mental health throughout the year.

SAD is caused by a disruption to our circadian rhythms

SAD is related to mismatches in our circadian rhythms and external cues such as timing around sleep and awakening. We all have hormones that cycle throughout the day depending on our biological clock. The decrease in light in wintertime can impact the body’s production of serotonin and melatonin, impacting sleep and mood.

SAD can impact people at any time of year

Most people develop seasonal affective disorder during late autumn and winter, when there is less light during the day. However, some people regularly experience depressive episodes in the summer or at other times throughout the year. Often, the symptoms of SAD are different depending on timing. Symptoms for winter SAD tend to differ from traditional depression, including an elevated appetite craving carbohydrates and increased sleep and time spent in bed. At the same time, more traditional symptoms including feeling sluggish and lost interest in usual activities can also be present.

Some people are at greater risk of SAD

There are a few factors that make individuals more likely to develop SAD. It is more common in people who have a family history of SAD and individuals with bipolar disorder are at greater risk. It’s most common among people in their 20s and 30s. Additionally, individuals living at higher northern latitudes are more susceptible, likely because there is less light.

SAD is different from the “Holiday Blues”

Some people experience a rise in depression around the holidays, often feeling their worst right after the holidays end. This is known as the Holiday Blues and is most often brought on by painful reflection and loneliness as well as the extreme emotions and demands around the holidays that can cause stress and anxiety. Holiday Blues are different from SAD both in terms of timing and causes.

Light is an effective treatment for SAD

For many individuals, the best treatment for SAD is light therapy, also known as phototherapy. Psychiatrists will recommend individuals suffering from SAD sit one or two feet in front a light box for 30 minutes a day. This is typically most effective soon after waking in the morning, though it can vary depending on the individual. The good news is phototherapy can improve symptoms in the first week of use. What’s more, this kind of light therapy has been shown to be effective in treating other types of depression. Other treatments for SAD include antidepressants and cognitive behavioral therapy sessions.

You should not ignore symptoms of SAD

Like other kinds of mental health conditions, the need for treatment of SAD will depend on how much it’s impacting your life. It’s important to be aware of changes in your mood throughout the year and to talk to your doctor or a psychiatrist if your daily life is being affected or if you’re having suicidal thoughts.

If you (or a person you know) are thinking or talking about killing yourself, reach out to suicide prevention resources. Many places offer emotional support to people in suicidal crisis or emotional distress. Trained mental health professionals can

• Offer positive solutions to the problem that brought on the crisis
• Remind you that you have family members and friends who care and want to help
• Arrange for in-person emergency help

For more about SAD, visit the Manuals page on depression.